There may not be a definitive answer.

Some arguments for using fewer, larger cards:

• Less card swapping. When using small cards, you could potentially miss the shot because you have to swap cards.
• Lower chance of user error. If you have a dozen cards then keeping track of formatted cards, used cards, backed-up cards... is a disaster waiting to happen.

And for more, smaller cards:

• If you swap cards frequently, losing a single card due to loss/theft/failure is a lower total loss as a percent of all photos.

As mentioned by @Olivier, failure is a low probability event, but the flip-side is that failure is a high impact event! Note that manufacturer lifetime estimates are based on a large sample; an individual card could fail after one more use, and you'd have no way of knowing beforehand. If you only have one card with you, that could be a catastrophic failure (for you). We've all heard stories of even good quality cards failing while still new.

Theft/loss is a tricky one. If someone steals all your gear, then the number of cards makes no difference. However, if someone steals all your gear that you have on you at that point in time, and the bulk of your cards are safely locked in your hotel room, then you minimise your loss. Other examples could be if you fall off a boat and your gear floats away/sinks - same argument.

My approach: I have multiple big cards. Big enough that I won't run out mid-shoot. And enough cards that I can change as often as required, and leave the used cards safely locked away somewhere.